return err
}

// Peek returns the next n bytes without advancing the reader. The bytes stop
// being valid at the next read call. If Peek returns fewer than n bytes, it
// also returns an error explaining why the read is short. The error is
// [ErrBufferFull] if n is larger than b's buffer size.
//
// Calling Peek prevents a [Reader.UnreadByte] or [Reader.UnreadRune] call from succeeding
// until the next read operation.